Effects of pre-severance irradiance on the growth of Allanblackia floribunda Oliv. stockplants and on the subsequent rooting capacity of leafy stem cuttings

The rooting of Allanblackia stem cuttings is typically slow and with the formation of very few roots. Irradiance has positive effects on the relative growth of plants and rooting ability, but there is no information relating to Allanblackia species. Stumps of Allanblackia floribunda Oliv. were grown under three levels of irradiance (2008 µmol m−2s−1, 542 µmol m−2s−1 and 160 µmol m−2s−1) and were assessed for growth (plant height and the number of cuttings) and the influence of irradiance on the rooting ability of leafy stem cuttings. Shade light regime 542 µmol m−2s−1 resulted in significantly greater stockplant height than in 160 and 2008 µmol m−2s−1. Significantly more useable cuttings were harvested from the tall plants under an irradiance of 542 µmol m−2s−1, fewer from 160 µmol m−2s−1, and the least from 2008 µmol m−2s−1. The rooting ability of cuttings was greatest from stockplants receiving 542 µmol m−2s−1 (> 60%) and least from those receiving 160 µmol m−2s−1 (20%). 45% of cutting rooted from stockplants under full sun (2008 µmol m−2s−1). The speed of rooting of cuttings followed the same ranking with the fastest rooting from plants receiving 542 µmol m−2s−1 (7.1 ± 1.04 weeks to reach 25% of rooting) and the slowest from those under 160 µmol m−2s−1 (12.3 ± 1.85 weeks to reach 25% of rooting). The results of this study demonstrate that the light management of A. floribunda stockplants is important for the maximization of the yielding of cutting and the speed of rooting of leafy stem cuttings. Tree plantation being a key option to alleviate environmental challenges that the world is facing today, these results confirm previous findings which postulates that appropriate light management in stockplants can increase the production speed of required seedlings.